The proposed work studies intravenous amphetamine and cocaine self-administration in rhesus monkeys. The effect of chlorpromazine and haloperidol administration on behavior maintained by these stimulants has been compared to similar behavior maintained by food. Stimulant self-administration is much more resistant to the disrupting effects of the neuroleptics than is food-reinforced behavior. The proposed work will attempt to clarify the nature of this differential effect and to determine whether neuroleptics are altering the ability of the stimulants to reinforce behavior.